The passenger pigeon (Ectopistes migratorius), also known as the wild pigeon, is an extinct North American bird. Named after the French word passager which means "passing by", the bird was one of the most plentiful species in the Americas, if not the world, with some flocks containing over a billion individuals. One flock, according to southern Ontario residents in 1866, apparently held in excess of 3.5 billion birds, measured a mile wide and 300 miles long, and took 14 hours to pass.

The earliest passenger pigeon fossils date back to the late Pleistocene epoch, and thrived throughout the Holocene epoch until the early 20th century, where the genus' population drastically declined due to habitat destruction and excessive hunting.